1. Field of the Invention
This invention relates to a sheet sorter with a stapler, and more particularly to a sheet sorter which is provided with a plurality of bins each of which receives a plurality of sheets discharged from an image recording apparatus such as a printer, a copier or the like and forms thereon a stack of sheets, and a stapler for stapling or binding the sheet stack on each bin.
2. Description of the Related Art
As disclosed, for instance, in Japanese Unexamined Patent Publication No. 4(1992)-43089, there has been known a sheet sorter in which a plurality of recorded sheets discharged from an image recording apparatus such as a printer, a copier or the like are distributed to a plurality of bins or sort trays in sequence to form a stack of sheets on each bin by a sheet distributor called an indexer and when the number of the sheets stacked on each of the bins reaches a predetermined value, the sheet stack on each of the bins is stapled by a stapler which is movable up and down along the array of the sheet inlet ends of the bins and in a horizontal direction along the edge of each bin (direction of width of the sheets).
Accordingly when stapling the sheet stack, it is necessary to eject the sheet stack on selected one of the bins toward the stapler beyond the sheet inlet end of the bin by a predetermined length. Further it is necessary to provide a reciprocal pusher member which pushes the stapled sheet stack back to the bin so that the stapled sheet stack does not interfere with the stapler in moving to a next sheet stack.
In order to push right the sheet stack so that the sheet stack is returned to the bin straight, it is preferred that the reciprocal pusher member be caused to act on the trailing edge of the sheet stack at the middle thereof. However since the sheets are various in size and at the same time the sheet stack on the bin is generally shifted toward one side of the bin so that a predetermined side edge of the sheet stack is in contact with a predetermined reference surface irrespective of the size of the sheets, it is impossible to cause a single fixed reciprocal pusher member to act on the trailing edge of the sheet stack at the middle thereof irrespective of the size of the sheets.
Conventionally, a plurality of reciprocal pusher members are arranged in the direction of width of the sheet at predetermined intervals in order to push right the sheet stack so that the sheet stack is returned to the bin straight.